Vertical axis wind turbines have an ancient history going back to Persian windmills of the first millennium. By the end of the nineteenth century and early 20th century numerous designs were conceived for vertical axis windmills that incorporate a series of exterior vanes to deflect the wind entering the turbine and enhance its performance.
Prior art patents of this type include:
Cleland U.S. Pat. No. 204,481 PA1 Bouteiller U.S. Pat. No. 343,000 PA1 Evison U.S. Pat. No. 591,962 PA1 Hensel U.S. Pat. No. 683,935 PA1 Bey U.S. Pat. No. 964,374 PA1 Liston U.S. Pat. No. 1,015,695 PA1 Sterner U.S. Pat. No. 1,144,737 PA1 Cain U.S. Pat. No. 1,127,400 PA1 Adams U.S. Pat. No. 1,441,774 PA1 Webb U.S. Pat. No. 1,619,643 PA1 Carter U.S. Pat. No. 3,793,530 PA1 Mogoveny et al U.S. Pat. No. 3,938,907 PA1 Sellman U.S. Pat. No. 4,017,204 PA1 Bartsch U.S. Pat. No. 4,725,194 PA1 DeMenezes U.S. Pat. No. 4,872,804
Generally, these patents address such features as speed-control governors. The turbine buckets or troughs that serve as impellers are either open or closed, according to whether the wind may flow past such buckets into the interior region of the turbine, around its vertical axis. The exterior vanes in these references are angled to direct wind more nearly perpendicularly into the receiving face of the rotating buckets, and to shield the returning impellers from exposure to the wind. As depicted in the references, these deflecting exterior vanes are all formed of single sheets of curved metal or the like.
Further more recent patents include the following:
Of these references, several show "funnelling" features leading up to the turbine inlets to concentrate and speed-up the wind as it enters the turbine impellers. As well, the exterior vanes mentioned previously intrinsically serve to concentrate the wind as they extend between outer and inner cylindrical openings and close together in a normal, radial-like manner.
Generally, the vertical series of known wind-receiving impellers and the outer encircling array of deflector vanes are held in place by respective pairs of end plates to which the ends of these components are fastened. The axis of the turbine itself is generally fitted into the upper plate which caps the deflector vanes and frames the turbine. As the force of the wind will develop a substantial toppling torque on the entire turbine structure, it is important that this outer frame formed by the deflector vanes and their end plates will constitute a rigid and stable structure.
This is all the more so true because the preferred aspect ratio for a vertical wind turbine will provide for a height that is greater than its width (providing for more wind-receiving surfaces in an elevated position). Thus, the stabilization of the outer deflector frame is akin to the problem of supporting a relatively small roof with an encircling series of relatively lengthy columns and providing strength to resist lateral wind forces.
The present invention provides an improvement in this structural support aspect of vertical axis wind turbines. As a further feature, this invention improves the performance of such turbines by increasing the concentration effect of air entering the turbine. Additionally, the air entering the turbine buckets or troughs is contained momentarily in a manner which further contributes to the performance of the turbine. Lastly, an improved method of extracting the rotary power is provided. These and other features of the invention will become apparent from its description.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.